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Effects of heliox as carrier gas on ventilation and oxygenation in an animal model of piston-type HFOV: a crossover experimental study

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Objective This study aimed to compare gas exchange with heliox and oxygen-enriched air during piston-type high-frequency oscillatory ventilation (HFOV). We hypothesized that helium gas would improve both carbon dioxide elimination and arterial oxygenation during piston-type HFOV. Method Five rabbits were prepared and ventilated by piston-type HFOV with carrier 50% helium/oxygen (heliox50) or 50% oxygen/nitrogen (nitrogen50) gas mixture in a crossover study. Changing the gas mixture from nitrogen50 to heliox50 and back was performed five times per animal with constant ventilation parameters. Arterial blood gas, vital function and respiratory test indices were recorded. Results Compared with nitrogen50, heliox50 did not change PaCO 2 when stroke volume remained constant, but significantly reduced PaCO 2 after alignment of amplitude pressure. No significant changes in PaO 2 were seen despite significant decreases in mean airway pressure with heliox50 compared with nitrogen50. Conclusion This study demonstrated that heliox enhances CO 2 elimination and maintains oxygenation at the same amplitude but with lower airway pressure compared to air/O 2 mix gas during piston-type HFOV.

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Published 01 January 2010
Reads 10
Language English
Zeynalovet al.BioMedical Engineering OnLine2010,9:71 http://www.biomedicalengineeringonline.com/content/9/1/71
R E S E A R C HOpen Access Effects of heliox as carrier gas on ventilation and oxygenation in an animal model of pistontype HFOV: a crossover experimental study 1,2 11* Bakhtiyar Zeynalov, Takehiko Hiroma , Tomohiko Nakamura
* Correspondence: tnakamura@naganoch.gr.jp 1 Division of Neonatology, Nagano Childrens Hospital, Azumino City, Nagano, Japan
Abstract Objective:This study aimed to compare gas exchange with heliox and oxygen enriched air during pistontype highfrequency oscillatory ventilation (HFOV). We hypothesized that helium gas would improve both carbon dioxide elimination and arterial oxygenation during pistontype HFOV. Method:Five rabbits were prepared and ventilated by pistontype HFOV with carrier 50% helium/oxygen (heliox50) or 50% oxygen/nitrogen (nitrogen50) gas mixture in a crossover study. Changing the gas mixture from nitrogen50 to heliox50 and back was performed five times per animal with constant ventilation parameters. Arterial blood gas, vital function and respiratory test indices were recorded. Results:Compared with nitrogen50, heliox50 did not change PaCO2when stroke volume remained constant, but significantly reduced PaCO2after alignment of amplitude pressure. No significant changes in PaO2were seen despite significant decreases in mean airway pressure with heliox50 compared with nitrogen50. Conclusion:This study demonstrated that heliox enhances CO2elimination and maintains oxygenation at the same amplitude but with lower airway pressure compared to air/O2mix gas during pistontype HFOV.
Background Helium is a noble gas with very low atomic weight (4 g/mol) and density (0.18 g/L). When mixed with oxygen as heliox, the low density of helium reduces the resistance associated with gas delivery. This increased mobility has three effects: gas more readily reaches the alveoli, allowing greater diffusion; breathing effort is significantly reduced with use of a lessdense gas; and carbon dioxide (CO2) is eliminated more rapidly [15]. Highfrequency oscillatory ventilation (HFOV) offers a tempting advantage in main taining oxygenation using higher mean airway pressure with minimal risk of complica tions. HFOV has been used in a variety of clinical situations, including neonatal respiratory distress syndrome, congenital diaphragmatic hernia, meconium aspiration syndrome, and air leak syndrome. Heliox has been reported as beneficial with various forms of nonconventional ventilation, including HFOV, highfrequency jet ventilation (HFJV), and highfrequency percussive ventilation. Winters et al. described a case series of 5 pediatric patients who showed marked improvements in ventilation with the use of heliox during HFOV [6]. Gupta et al. reported combined use of heliox and HFJV to
© 2010 Fakhraddin et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.